The first wife of Peter Cook has broken her silence to tell of her sorrow at how alcoholism and depression undermined his principles and destroyed his talent. Wendy Cook, the mother of the comedian's two children, said she still regrets she was not able to help her husband when he began to drift into heavy drinking.

'I just wish we had both been wiser then,' she told The Observer this weekend. 'He really suffered. Nobody as sensitive as he was could help but suffer. Genius is also torture.'

His descent into alcoholic dependency, depression and promiscuity were, she now believes, a result of his emotional vulnerability. As their relationship ended in the mid-Sixties, she claims his youthful ideals were soon replaced by a 'lower side of his character'. This was the side which produced the Derek and Clive tapes, the obscene underground cult hits recorded by Dudley Moore and Cook in the Seventies which she regards as evidence of Cook's bleak decision to take the wrong 'route' in life.

'He had gone way, way away from his original idealism,' she said. 'He was a very upright sort of person when I was first with him. At that point he even thought he had a career in the Foreign Office ahead of him, but something started to rot inside. I hear it was drugs too.'

The couple met when Cook was a charismatic young undergraduate at Cambridge University and Wendy Snowden, as she was then known, was studying art in the city. Admired by many students for her fashion sense and bohemian manners, she and Cook began living together just as his mischievous satire grabbed the attention of London's theatrical talent scouts.

The critical popularity of his student revue with the Footlights eventually led to the West End hit Beyond the Fringe , also starring Moore, alongside their young contemporaries Alan Bennett and Jonathan Miller. In 1963, after the show had successfully transferred to Broadway, Cook and Snowden were married in New York.

The glamorous couple were also courted by many of the most important personalities in America, but it was not long before their relationship became troubled. 'I left to live in Majorca because I didn't like the media world in London. And, of course, if you just go and leave an attractive and brilliant man alone, it is pretty obvious that something is going to happen,' she said, referring to Cook's affair with Judy Huxtable, the actress who became his second wife in 1973.

'It is pointless to have regrets, but I do wish I could have been wiser. I could have behaved differently, particularly as young children were involved.'

This autumn Cook agreed to take part in a BBC documentary about her former husband and to speak publicly about her life with him. In At a Slight Angle to the Universe: The Story of Peter Cook , to be broadcast this month, she describes the breakdown of the marriage for the first time. 'It was clear that he had Judy in his life and I wasn't prepared to have a shared relationship. It all very quickly went dark,' she explains, clearly moved by the memory.

Wendy Cook's decision to talk about her ex-husband for the first time followed discus sions with his sisters and with their daughters - Lucy, now a 37-year-old aromatherapist, and Daisy, a 36-year-old artist.

'They urged me to do it,' said Wendy, who concedes that it has been an unexpectedly emotional experience. 'It was such a long time ago, but it did start to excavate the memories and now it all seems quite near to me. It was terrible after we split to see someone on television, who you once knew so well, now so removed, and to see what they were doing and to feel so helpless.'

After a series of television hits and an acclaimed partnership with Dudley Moore, Cook's drinking began to have an impact on his work and on his second marriage. After a turbulent Australian tour, Moore finally broke away from Cook and went on to develop a profitable solo career in film. In 1989, Cook divorced Judy, marrying Lin Chong later that year.

Wendy says she felt privileged to have watched Moore and Cook writing sketches together in the Sixties. 'I think Peter loved Dudley more than anyone else in his life,' she says.

Researchers on the documentary have also unearthed the only known recording of Peter Cook's failed attempt at becoming a chat show host. In 1973 the BBC's Where Do I Sit? was badly panned by the critics and pulled after only three editions. Friends, including former Python Eric Idle, believe this blow hastened the decline into alcoholism. 'The critics said he wasted his life,' Idle says. 'In fact, they tried to waste him.'

Eight years ago, after suffer ing a stomach haemorrhage, Cook died at the age of 57. Lin Chong Cook did not invite Wendy Cook to the funeral.

Cook, now a food writer, says she is resigned to the idea that the story will be repeatedly retold. 'If you are a genius, then people will go on wanting to understand you,' she said. 'I knew him like nobody else did. Each person brings a different symphony out of someone.'

The following correction was printed in the Observer's For the Record column, Sunday December 15, 2002

This interview with Wendy Cook gave the impression that their relationship was in difficulty by the mid-Sixties. In fact, they remained a couple for another five years, divorcing in 1971.